The three biogenic amines, serotonin, norepinephrine and dopamine are most closely linked to CNS disorders such as depression. The majority of antidepressants in current use selectively inhibit the reuptake of serotonin and/or norepinephrine. Although a strong dopamine re-uptake inhibiting activity is considered with the risk of undesirable central stimulation effects, many reports have disclosed that the triple monoamine neurotransmitter, i.e serotonin, norepinephrine and dopamine re-uptake inhibitors are useful for the treatment of CNS disorders such as depression, anxiety, attention deficit hyperactivity disorder, obesity, drug addiction and pain disorder. For example, International Patent Application No. WO 2004/072071 discloses the novel 8-aza-bicyclo[3,2,1]octane derivatives useful as monoamine neurotransmitter re-uptake inhibitors.
3-Substituted piperidine compounds are effectively used for controlling various central nervous system (CNS) disorders. For example, International Patent Application No. WO 02/51837 discloses 3-substituted piperidine derivatives that are suitable for treating anxiety, depression, sleep disorder. Active research and development efforts have continued to be directed to the application of 3-substituted piperidine compounds for the treatment of CNS disorders.